The present invention relates to a motor vehicle braking system, comprising a brake carrier, which has at least one bore defining a first longitudinal axis, and a guide pin, which is arranged in the bore and is configured to slidably support the brake caliper relative to the brake carrier, wherein the guide pin defines a second longitudinal axis, wherein the disc brake arrangement further comprises a protective bellows, which at least partially surrounds regions of the guide pin protruding from the bore.
Disc brake arrangements of this kind with a protective bellows are known from the prior art. Here the protective bellows serves in particular to seal the guide pin and the bore in the brake carrier from the environment. The protective bellows can also have a damping effect on the displacement movements of the guide pin, in order, for example, to avoid an audible metallic striking of the guide pin against the brake carrier caused by a functional play between guide pin and the bore in the brake carrier.
The document DE 10 2011 017 220 A1 discloses in this regard an exemplary solution, which is shown in FIGS. 2 to 4 of the present document. As is recognized in FIG. 2, in this solution a guide pin 10 is formed with a head region 12, from which a cylindrical shaft region 14 extends along a guide pin longitudinal axis L2. The shaft region 14 is taken up for the most part in a bore 16 in a brake caliper 18 shown in a partial sectional view and is guided displaceably therein. The bore 16 defines a bore longitudinal axis L1, which coincides in the case shown with the guide pin longitudinal axis L2. In other words, the guide pin 12 with its shaft region 14 is taken up concentrically in the bore 16. Here the guide pin 12 protrudes in a known manner by a different extent from the bore 16 depending on the current operating state of the disc brake arrangement.
In FIG. 2 a protective bellows 20 is also shown, which is shown in FIGS. 3 and 4 in a single component view and in a partial sectional view. The protective bellows 20 has a first mounting section 22, which is mounted on the brake carrier 18 in a sealing manner in a recess 23. At its end lying axially opposite the mounting section 22, the protective bellows 20 has a second mounting section 24, which is mounted in the region of the head section 12 on the guide pin 10 in a sealing manner.
A detailed description of such a mounting solution by means of the sections 22 and 24 can be found in the document DE 20 2006 006 142 U1.
The two mounting sections 22, 24 are substantially configured ring-shaped and arranged concentrically to one another. A longitudinal axis L0 of the protective bellows 20 extends through the respective center points of their ring-shaped cross sections. Furthermore, the mounting sections 22, 24 are connected by a deformation section 25 arranged in between in the form of a folding bellows, which is generally formed as a cylinder and likewise extends concentrically about the protective bellows longitudinal axis L0. The protective bellows 20 thus surrounds the regions of the shaft portion 14 of the guide pin 10 that protrude from the bore 16 and follows their displacement movements via the second mounting section 24 with a deformation of the deformation section 25.
The protective bellows 20 further has a guide portion 26, which takes up a part of the shaft portion 14 of the guide pin 10 displaceably. As is recognized in FIGS. 3 and 4, the guide portion 26 is configured as a substantially cylindrical section of the protective bellows 20 that extends with a symmetrical cross section about a longitudinal axis L3. It is further recognized that the guide portion 26 is arranged inside the first mounting section 22, which has a larger diameter. In the case shown, the guide portion 26 is arranged concentrically to the mounting sections 22, 24 and the deformation section 25, so that the protective bellows longitudinal axis Lo and the guide portion longitudinal axis L3 coincide. The guide portion 26 is also taken up in some sections in a recess 27 in the brake carrier.
In its inner circumferential region 28, the guide portion 26 has a contact surface 30, which is configured with grooves 32 and recesses 34 for adjusting the sealing and friction properties in guiding of the guide pin 10. The guide pin 10 is guided here in the protective bellows 20 in such a way that the guide pin longitudinal axis L2 and the protective bellows and guide portion longitudinal axis L0, L3 coincide. Overall the guide portion 26 and the bore 16 are thus arranged as a whole in this solution in alignment or concentrically to one another, so that the guide portion longitudinal axis L3 and the bore longitudinal axis L1 also coincide.
It is generally advantageous if the guide pin is taken up in the bore with a certain functional play, in order to prevent seizing up. This concerns in particular a functional play transverse to the longitudinal axes of guide pin and bore. In other words, it is desirable if the guide pin is transversely or radially movable to a certain degree inside the bore. This makes it possible, for example, for the guide pin to get out of the way temporarily in such a direction in the event of a dynamic shift. As in the case discussed above, solutions in particular with guide pins guided concentrically in a bore with a uniformly circumferential radial guide play in a peripheral direction are known for this.
The document DE 197 10 690 A1 describes a disc brake with a sliding guide mechanism, which comprises a main guide pin and a subsidiary guide pin, which are each taken up axially movably in a guide hole. The subsidiary guide pin is arranged on a run-in side of a brake disc, while the main guide pin is arranged on the run-out side of the brake disc. Furthermore, rubber sleeves are provided on sections of the guide pins that protrude from the openings of the guide holes to repel water and dust. The subsidiary guide pin has a smaller diameter than the guide hole which takes up the subsidiary guide pin, so that the subsidiary guide pin is also movable radially in the guide hole. When braking is carried out, the subsidiary guide pin is pressed due to this by the forces transmitted by the brake disc against the inner diameter of the associated guide hole, whereby vibrations should be limited.
Further prior art is known from the document DE 25 14 383 A1, which describes a vehicle disc brake with a sliding connection between a caliper and a brake carrier, wherein the sliding connection comprises two pins. The pins are each taken up movably in an aperture that is formed oversized. The pins are further provided in some sections with sealing sheaths, which protect the sliding surfaces of the pins. A leaf spring is arranged between a crown part of the caliper and retaining plates of friction linings and pretensions the pins in an eccentric position in the respective openings.
In solutions of this kind, however, it has been shown that various disruptive influences can arise in the guiding of the guide pin in the bore of the brake carrier, which obstruct quiet operation of the disc brake, and this may be found disturbing by a vehicle operator. In particular, striking of the guide pin against the inner circumferential surface of the bore can occur in certain situations in the event of a displacement of the guide pin within the functional play provided. Friction vibrations between the brake lining and the brake disc can also be transmitted to the guide pin in this case and lead to pulsing movements and corresponding noises.